[libcxx-commits] [PATCH] D118329: [libc++] Optimize algorithms on uninitialized memory for trivial types.

[Konstantin Varlamov via Phabricator via libcxx-commits]

var-const created this revision.
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There are five cases (also applying to the `*_n` versions of the
algorithms):

- `destroy` is a no-op when the type is trivially destructible;
- `uninitialized_default_construct` is a no-op when the type is trivially default-constructible and destructible;
- `uninitialized_value_construct` zeroes out trivially default constructible types using  `memset`;
- `uninitialized_fill` uses `memset` if both types are trivial and 1-byte long;
- `uninitialized_copy` and `uninitialized_move` use `memcpy` on trivially copy-constructible types.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D118329

Files:
  libcxx/include/__bit/bit_cast.h
  libcxx/include/__memory/construct_at.h
  libcxx/include/__memory/uninitialized_algorithms.h
  libcxx/include/memory
  libcxx/include/type_traits
  libcxx/test/std/utilities/memory/specialized.algorithms/buffer.h
  libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/destroy.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/destroy_at.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/destroy_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/ranges_destroy.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/ranges_destroy_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.default/ranges_uninitialized_default_construct.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.default/ranges_uninitialized_default_construct_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.default/uninitialized_default_construct.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.default/uninitialized_default_construct_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.value/ranges_uninitialized_value_construct.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.value/ranges_uninitialized_value_construct_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.value/uninitialized_value_construct.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.construct.value/uninitialized_value_construct_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.copy/ranges_uninitialized_copy.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.copy/ranges_uninitialized_copy_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.copy/uninitialized_copy.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.copy/uninitialized_copy_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.fill.n/ranges_uninitialized_fill_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.fill.n/uninitialized_fill_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.fill/ranges_uninitialized_fill.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.fill/uninitialized_fill.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.move/ranges_uninitialized_move.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.move/ranges_uninitialized_move_n.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.move/uninitialized_move.pass.cpp
  libcxx/test/std/utilities/memory/specialized.algorithms/uninitialized.move/uninitialized_move_n.pass.cpp

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